Gas turbomachine including a purge flow reduction system and method

ABSTRACT

A gas turbomachine includes a turbine portion including at least one turbine wheel, and a wheel shaft operatively connected to the at least one turbine wheel. The wheel shaft includes an outer surface. A stationary member includes an inner surface positioned outward of the outer surface of the wheel shaft to form a purge flow passage. A bearing housing is linked to the stationary member and spaced radially outward of the wheel shaft. The bearing housing includes at least one purge flow passage configured and disposed to guide a purge flow toward the wheel shaft. At least one of the outer surface of the wheel shaft and the inner surface of the stationary member includes a roughness inducing coating configured and disposed to increase drag and residence time of purge flow in the purge flow passage.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to the art of gasturbomachines and, more particularly, to a gas turbomachine including apurge flow reduction system.

Many turbomachines include a compressor portion linked to a turbineportion through a common compressor/turbine shaft or rotor and acombustor assembly. The compressor portion guides a compressed air flowthrough a number of sequential stages toward the combustor assembly. Inthe combustor assembly, the compressed air flow mixes with a fuel toform a combustible mixture. The combustible mixture is combusted in thecombustor assembly to form hot gases. The hot gases are guided to theturbine portion through a transition piece. The hot gases expand throughthe turbine portion rotating turbine blades to create work that isoutput, for example, to power a generator, a pump, or to provide powerto a vehicle. In addition to providing compressed air for combustion, aportion of the compressed airflow is passed through the turbine portionfor cooling purposes. Additional cooling/heating is provided byintroducing purge flows from the turbine portion into various regions ofthe turbomachine. For example, purge flows are often employed tocool/heat aft portions of the turbine. The purge flow also helps tomaintain desired thermal expansion of adjacent parts

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the exemplary embodiment, a gas turbomachineincludes a turbine portion including at least one turbine wheel, and awheel shaft operatively connected to the at least one turbine wheel. Thewheel shaft includes an outer surface. A stationary member includes aninner surface positioned outward of the outer surface of the wheel shaftto form a purge flow passage. A bearing housing is linked to thestationary member and spaced radially outward of the wheel shaft. Thebearing housing includes at least one purge flow passage configured anddisposed to guide a purge flow toward the wheel shaft. At least one ofthe outer surface of the wheel shaft and the inner surface of thestationary member includes a roughness inducing coating configured anddisposed to increase drag and residence time of purge flow in the purgeflow passage.

According to another aspect of the exemplary embodiment, turbomachinesystem includes a rotating component including an outer surface, astationary member including an inner surface positioned outward of theouter surface of the rotating component to form a fluid flow passage,and a bearing housing linked to the stationary member and spacedradially outward of the rotating component adjacent the stationarymember. The bearing housing includes at least one fluid flow passageconfigured and disposed to guide a fluid flow toward the fluid flowpassage. At least one of the outer surface of the rotating component andthe inner surface of the stationary member includes a roughness inducingcoating configured and disposed to increase drag and residence time offluid flow in the purge flow passage.

According to yet another aspect of the exemplary embodiment, a method ofdecreasing purge flow in a gas turbomachine includes guiding a purgeflow into a purge flow passage defined between a rotating component anda stationary member, and inducing the drag in the purge flow through aninteraction with a roughness inducing coating provided on one of therotating component and the stationary component. The drag leads to anincreased temperature and residence time of the purge flow in the purgeflow passage that reduces an amount of required purge flow.

These and other advantages and features will become more apparent fromthe following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF DRAWINGS

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification.

The foregoing and other features, and advantages of the invention areapparent from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIG. 1 is a partial cross-sectional view of an aft portion of a turbineportion of a gas turbomachine in accordance with an exemplaryembodiment;

FIG. 2 is a plan view illustrating a wheel shaft having a purge flowreduction system including a roughness inducing coating coupled to anaft turbine wheel in accordance with an exemplary embodiment; and

FIG. 3 is a partial perspective view of a bearing housing and a statorincluding a roughness inducing coating arranged at the aft portion ofthe turbine portion of FIG. 1.

The detailed description explains embodiments of the invention, togetherwith advantages and features, by way of example with reference to thedrawings.

DETAILED DESCRIPTION OF THE INVENTION

A gas turbomachine in accordance with an exemplary embodiment isindicated generally at 2 in FIG. 1. Gas turbomachine 2 includes aturbine portion 4 having a plurality of turbine wheels, one of which isindicated at 8 that supports rows of buckets (not shown) along a hot gaspath 11. Combustion gases flowing along hot gas path 11 impinge upon therows of buckets imparting a rotational force to turbine wheels 8. Thecombustion gases pass from hot gas path 11 into an exhaust cone 14supported by a housing 16.

Turbine wheel 8 is operatively coupled to a rotating component or wheelshaft 19. Wheel shaft 19 rotates in response to rotation of turbinewheel 8. Wheel shaft 19 includes an axial portion 22 having an axialportion outer surface 24 and an angled portion 28 having an angledportion outer surface 30. As shown in FIG. 2, a rabbet portion 33extends from angled portion 28 and joins with turbine wheel 8. Rabbetportion 33 includes a plurality of openings (not separately labeled)that receive mechanical fasteners, one of which is shown at 36.Mechanical fasteners 36 link wheel shaft 19 to turbine wheel 8. As willbe discussed more fully below, a stationary member or stator 40 and abearing housing 44 are supported from housing 16. Stator 40 is arrangedadjacent to angled portion 28, and bearing housing 44 is positionedadjacent to axial portion 22.

Stator 40 includes a first section 50 that extends to a second section51 and a third section 52. Second section 51 is angled to correspond toangled portion 28 of wheel shaft 19. Third section 52 extends generallyparallel to axial portion 22 of wheel shaft 19 and first section 50extends generally perpendicularly to third section 52. First section 50includes a first inner surface 54, second section 51 includes a secondinner surface 55, and third section 52 includes a third inner surface56. Bearing housing 44 includes a bearing housing body 60 including afirst end portion 62 that extends to a second end portion 63 through anintermediate portion 64. First end portion 62 supports a plurality ofseal members, one of which is indicated at 67. Seal members 67 preventlubricant and/or coolant (not shown) flowing along axial portion 22 topass toward angled portion 28. Seal member 67 is shown to include apurge flow nozzle 69 that passes a purge flow through bearing housing60. The purge flow passes into a purge flow passage 75 that extendsbetween angled portion outer surface 30 and first, second, and thirdinner surfaces 54-56 of stator 40. The purge flow may originate from acomponent operatively coupled to turbomachine 2 such as a compressor(not shown) or from an external source such as a blower (also notshown).

The purge flow is controlled to condition rabbet portion 33 to achieve arate of thermal expansion that aligns with a rate of thermal expansionof turbine wheel 8. During start up, blades mounted to turbine wheel 8are exposed to combustion gases flowing along hot gas path 11. As aresult, turbine wheel 8 thermally expands faster than rabbet portion 33.In order to offset the difference in rates of thermal expansion, a largeamount of purge flow is passed into purge flow passage 75 to causeangled portion 28 and rabbet 33 to heat up faster and match the rate ofthermal expansion of turbine wheel 8. The amount of purge flow passinginto purge flow passage 75 represents lost work that results inefficiency losses for turbine portion 4.

In accordance with the exemplary embodiment, turbine portion 4 includesa purge flow reduction system 88 that leads to a reduced amount of purgeflow required to heat rabbet 33. Purge flow reduction system 88 includesroughness inducing coating 90 provided on angled portion 28 and anotherroughness inducing coating 94 provided on second inner surface 55 ofstator 40. Roughness inducing coatings 90 and 94 induce a drag on thepurge flow in purge flow passage 75 that increases a residence time andtemperature of the purge flow. The increased residence time of the purgeflow leads to a reduction in the amount of purge flow required tocondition angled portion 28 and rabbet 33 to achieve a rate of thermalexpansion that more closely aligns with the rate of thermal expansion ofturbine wheel 8.

In accordance with one aspect of the exemplary embodiment, roughnessinducing coatings 90 and 94 comprise thermal or flame sprayed coatings98 and 100 respectively. Thermal coatings allow for the application of amelted or heated material to a substrate having a desired thickness. Thedesired thickness may be varied to achieve the desired drag andresidence time of the purge flow. Flame spray coating may includecoatings applied through a cold spray process. The roughness inducingcoating may be applied to one or the other of angled portion 28 orsecond inner surface 55 of stator 40. The overall surface area,thickness, and location of the roughness inducing coating may varydepending on the desired flow modification within purge flow passage 75.For example, the roughness inducing coating may entirely cover an entiresurface or may be applied in strips. Although described in terms ofbeing incorporated into a turbomachine, the roughness inducing coatingmay be employed in fluid passages of other systems to create a desiredrestriction.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

What is claimed is:
 1. A gas turbomachine comprising: a turbine portionincluding at least one turbine wheel; a wheel shaft operativelyconnected to the at least one turbine wheel, the wheel shaft includingan outer surface; a stationary member including an inner surfacepositioned outward of the outer surface of the wheel shaft to form apurge flow passage; and a bearing housing linked to the stationarymember and spaced radially outward of the wheel shaft, the bearinghousing including at least one purge flow passage configured anddisposed to guide a purge flow toward the wheel shaft, wherein at leastone of the outer surface of the wheel shaft and the inner surface of thestationary member includes a roughness inducing coating configured anddisposed to increase drag and residence time of purge flow in the purgeflow passage.
 2. The gas turbomachine according to claim 1, wherein theroughness inducing coating is provided on the outer surface of the wheelshaft.
 3. The gas turbomachine according to claim 1, wherein theroughness inducing coating comprises a flame sprayed coating.
 4. The gasturbomachine according to claim 1, wherein the wheel shaft includes anaxial portion and an angled portion, the angled portion being angledrelative to the axial portion and operatively connected to the at leastone turbine wheel.
 5. The gas turbomachine according to claim 4, whereinthe roughness inducing coating is provided on the angled portion of thewheel shaft.
 6. The gas turbomachine according to claim 5, wherein theroughness inducing coating is provided on each of the angled portion ofthe wheel shaft and the inner surface of the stationary member.
 7. Aturbomachine system comprising: a rotating component including an outersurface; a stationary member including an inner surface positionedoutward of the outer surface of the rotating component to form a fluidflow passage; and a bearing housing linked to the stationary member andspaced radially outward of the rotating component adjacent thestationary member, the bearing housing including at least one fluid flowpassage configured and disposed to guide a fluid flow toward the fluidflow passage, wherein at least one of the outer surface of the rotatingcomponent and the inner surface of the stationary member includes aroughness inducing coating configured and disposed to increase drag andresidence time of fluid flow in the fluid flow passage.
 8. Theturbomachine system according to claim 7, wherein the roughness inducingcoating is provided on the outer surface of the rotating component. 9.The turbomachine system according to claim 7, wherein the roughnessinducing coating comprises a flame sprayed coating.
 10. The turbomachinesystem according to claim 7, wherein the roughness inducing coating isprovided on each of the outer surface of the rotating component and theinner surface of the stationary member.
 11. A method of decreasing purgeflow in a gas turbomachine, the method comprising: guiding a purge flowinto a purge flow passage defined between a rotating component and astationary component; and inducing drag in the purge flow through aninteraction with a roughness inducing coating provided on one of therotating component and the stationary component, the drag leading to anincreased temperature and residence time of the purge flow in the purgeflow passage that decreases an amount of required purge flow.
 12. Themethod of claim 11, wherein inducing the drag in the purge flow includespassing the purge flow across a flame sprayed coating on an outersurface of the rotating component.
 13. The method of claim 11, whereininducing the drag in the purge flow includes passing the purge flowacross a flame sprayed coating provided on an outer surface of therotating component and an inner surface of stationary component.